This application relates generally to a method for the production of polymers having at least one unit containing at least one cyclopentanone structure condensed with at least two aromatic rings by electrolyzing aromatic compounds that have at least one cyclopentane structure condensed with at least two aromatic rings, or by electrolytic or chemical oxidation of polymers that have at least one unit containing at least one cyclopentane structure condensed with at least two aromatic rings, and more particularly to a method for the electrolysis of fluorene or its derivatives, and for the oxidation of poly(fluorene) or its derivatives, to poly(9-fluorenone) or its derivatives.
Isomers of poly(9-fluorenone), such as 2,7-poly(9-fluorenone), may be employed in bi/multilayer light-emitting diodes (LED) operated with Mg as a cathode. Uckert, F. et. al., Advanced Materials, Vol. 12, No. 12, p.p. 905-908 (2000). However, poly(9-fluorenone) has proven difficult to prepare, in particular, 9-fluorenone does not appear to have been electrolytically polymerized to date. Zecchin, S., et al., Journal of Electroanalytical Chemistry, Vol. 215, p.p. 377-383 (1986).
Currently, there are two main methods for preparing poly(9-fluorenone), and in particular, 2,7-poly(9-fluorenone). One method uses five separate and distinct steps, starting from malonic ester. The malonic ester is treated to produce 2,2-dioctylmalonic ester and in a separate step subsequently reduced with lithium aluminum hydride to provide a diol compound, 2,2-dioctyl-1,3-propanediol. The diol compound is then combined with 2,7-dibromo(9-fluorenone) which must be produced from fluorene in two separate steps. The result of the combination of the diol with the 2,7-dibromo(9-fluorenone), under appropriate conditions, is 2,7-dibromo-spiro(4xe2x80x2,4xe2x80x2-dioctyl-2xe2x80x2,6xe2x80x2-dioxocyclohexane-1xe2x80x2,9-fluorene). The 2,7-dibromo-spiro(4xe2x80x2,4xe2x80x2-dioctyl-2xe2x80x2,6xe2x80x2-dioxocyclohexane-1xe2x80x2,9-fluorene) is polymerized with a nickel catalyst to provide 2,7-poly(spiro(4xe2x80x2,4xe2x80x2-dioctyl-2xe2x80x2,6xe2x80x2-dioxocyclohexane-1xe2x80x2,9-fluorene)). The 2,7-poly(spiro(4xe2x80x2,4xe2x80x2-dioctyl-2xe2x80x2,6xe2x80x2-dioxocyclohexane-1xe2x80x2,9-fluorene)) is treated with dichloroacetic acid to give the final product, 2,7-poly(9-fluorenone). Uckert, F., et al., Macromolecules, Vol. 32, No. 14, p.p. 4519-4524 (1999).
In a second method for preparing poly(9-fluorenone), 2,7-dibromo-9-fluorenone, obtained by a two-step process from fluorene, is converted to Ni(PPh3)2(2-bromo-7-fluorenonyl)Br, which is then reduced electrochemically to give 2,7-poly(9-fluorenone). Zecchin, S., et al., Journal of Electroanalytical Chemistry, Vol. 215, p.p. 377-383 (1986).
Each method requires several separate steps and both have proven to be complicated and troublesome, involving the use of many potentially hazardous chemicals. Further, the methods have generally resulted in low polymer yields and high levels of impurities or byproducts.
Recently, Zecchin et al. alleged that 2,7-poly(9-fluorenone) films could be obtained from 2,7-poly(fluorene) films via oxidation with electrochemically generated superoxide. Zecchin, S., et al., Journal of Electroanalytical Chemistry, Vol. 215, p.p. 377-383 (1986). The report, however, provided no analysis of the film material to support the findings and Uckert et al. (Macromolecules, Vol. 32, No. 14, p.p. 4519-4524 (1999)) has disputed that the polymer obtained was in fact 2,7-poly(9-fluorenone), based on inconsistencies within Uckert""s data. Therefore, it is unclear if the Zecchin described superoxide method has utility for preparing poly(9-fluorenone).
As such, the methods for preparing poly(9-fluorenone) have proven to be of limited value. Accordingly there is a need for a simple and cost-effective method for producing poly(9-fluorenone) as well as other polymers having cyclopentanone structures. Against this backdrop the present invention has been developed.
Embodiments of the present invention include the electrolytic production of polymers wherein each polymer contains at least one unit having at least one cyclopentanone structure condensed with at least two aromatic rings. The method includes the electrolysis of a starting material in the presence of an ester. The particular polymer produced by the methods of the present invention depends on the starting material. The starting materials are aromatic compounds that have at least one cyclopentane structure condensed with at least two aromatic rings. Such materials are polymerized and the cyclopentane structure is oxidized into a cyclopentanone structure by methods of the present invention.
One example of an embodiment of the present invention is a method for producing poly(9-fluorenone) by electrolysis of fluorene in the presence of an ester. Embodiments of the method include passing an electric current through an electrolytic mixture comprising fluorene, an ester, and an electrolyte. Note that, depending on the ester, electrolyte, and reaction conditions, an additional solvent may be included in the electrolytic mixture to dissolve the ester, fluorene or electrolyte, or to increase the yield of the poly(9-fluorenone).
Polymers containing at least one unit that has at least one cyclopentane structure condensed with at least two aromatic rings may also be used as a starting material. In embodiments using polymers as starting materials, the cyclopentane structures within the polymer are oxidized to the cyclopentanone structures. One example of this type of embodiment is a method for producing poly(9-fluorenone) from poly(fluorene) via electrolytic oxidation.
Additional embodiments of the present invention include a method of producing polymers containing at least one unit that includes at least one cyclopentanone structure condensed with at least two aromatic rings via chemical oxidation of polymer starting materials. One example of the chemical oxidation embodiments of the present invention is a method for producing poly(9-fluorenone) from poly(fluorene) via chemical oxidation with a chemically prepared oxidizing agent.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.